Audio professionals have very specific goals when presenting events. A wide-frequency spectrum in our audio program. Realistic dynamics. A bal-anced mix. Intelligibility. That’s a tough one. It’d be nice to make sure that our audience can appreciate the subtleties of the artist we represent, whether that be a snare drum hit, a quick run of guitar notes or a whisper. Unfortunately, as venue size increases, intelligibility typically decreases due to a multitude of factors, including increased reverb time, poor coverage and attentiveness (or lack thereof) on the part of the audience. You may have noticed that cream of the crop artists such as U2 recognize this issue and actually play their songs a hair slower in large venues to make up for the fact that the venue is messing with their clarity.
Speech experts maintain that understanding music is far easier than understanding speech for two basic reasons. One is that music tends to repeat in patterns, so even if you are hearing a song for the first time, there’s a good chance that your brain will identify the guitar (or even vocal) line when it repeats in the second chorus. The other reason is familiarity: When you attend a Garth Brooks concert, you already know the words to his songs, so even if you can’t really understand them by ear, your brain understands them by memory. When Mr. Brooks addresses the audience, maybe to tell a story or perhaps to plug a new record, he’s more difficult to grasp because you don’t know what he is going to say.
Given these issues, it’s actually more difficult to produce sound reinforcement for a comedian than it is for an annoyingly loud metal band. The success of a “spoken word” event in any venue is completely linked to an engineer’s ability to make certain that everyone in the venue can under-stand the speaker, whether they be a poet, a comedian or a politician (or all of the above). If you can’t get the joke, then the joke is on you, probably at a not-so-funny price.
This is where audio pros must come to the rescue, providing PA to clearly deliver The Word (whatever that may be) to the masses. All too often, PA systems either don’t really help or (yikes) worsen the situation. When we try to amplify a voice in house of worship or a public hall, we run the risk of creating two big problems. First, we risk ruining the localization of the performer. Loudspeakers are placed at various positions throughout a hall, none of which coincide with the location of the performer. You see someone 40 feet away speaking to you, but hear his or her voice three feet away and to your left. The other problem is that PA systems, in general, often produce a multitude of reflections and reverberation paths that did not exist prior to the amplification of sound, resulting in gross sonic variations. Loudspeakers must be carefully distributed, aimed and time aligned throughout the room in order to prevent a train wreck.
The Big Guns in the sound reinforcement that fight against blurred speech are steerable arrays, loudspeakers whose output may be beamed at a spe-cific area of an audience. Much like a line array is to music, there are several goals to a steerable loudspeaker array. (1) Make sure that the listener hears audio from only one cabinet at any time, (2) control the speaker’s dispersion so as to not increase reverberant reflections, and (3) ascertain that audio from two different arrays will not sum or cancel and create phase issues.
So how do we steer? In the old days when audio was recorded in stone tablets using a chisel, we built narrow columns and aimed them at specific sections of the audience. Quaint, but very inaccurate. Like everything else, we now do it digitally.
A few manufacturers have been addressing these issues. EAW’s Digitally Steerable Array series of loudspeakers feature multiple drivers in column-type enclosures. Each of the drivers has its own amplification and DSP with integral networking for control via PC. EAW provides a software app called DSA Pilot that enables the system designer to adjust the vertical dispersion of the cabinet from 15 to 120 degrees, and electronically aim the coverage +/- 30 degrees. Horizontal coverage is fixed at 120 degrees, allowing wide spacing of DSA cabs in installations where mounting loca-tions are sparse. The DSA230 is a one-way system with somewhat limited frequency response (78 Hz to 10 kHz) suitable for speech or background music apps while the DSA250’s frequency response extends out to 15 kHz for full-range applications.
Renkus-Heinz takes a somewhat different approach in their ICONYX Series of speakers, employing full-range coax drivers numbering from eight (in the IC8) up to 32 in the IC32. The IC16 can shape and steer audio ‘beams’ down to 400 Hz, while the IC32 takes that spec down to 200 Hz. A single ICONYX array allows shaping and aiming of up to 16 separate audio beams via onboard DSP controlled using a PC app called LobeWare. LobeWare electronically manipulates the drivers via DSP, allowing the user to adjust the beam’s shape and directivity, even after the ICONYX array has been installed. If it turns out a column was hung too low, that column’s acoustic center can be raised using software instead of by physically moving the array.
Way across the Atlantic in The Netherlands, a company called Duran Audio BV has introduced the AXYS Intellivox line of steerable arrays. The Intellivox DC and DS are columns each with an array of 4-inch drivers, onboard amplification and DSP. The DSX series are similar, but substitute horn-loaded tweeters for some of the four-inch drivers. These arrays feature AXYS’s Digital Directivity Control (DDC) multichannel array technology managed by WinControl software, allowing the vertical directivity of the columns to be altered, providing increased intelligibility in rever-berant spaces and consistent SPL regardless of distance from the array. The Intellivox V-90 employs passive filtering and a preset vertical opening angle with a minus four-degree steering angle. When mounted to a flat surface, the result is accurate coverage to the listening area and a reduction in out-of-phase reflections from the mounting surface.
By enabling the user to control the vertical dispersion pattern, steerable arrays help prevent unwanted reflections off ceilings and floors of a venue, which in turn reduces destructive interference and makes the message easier to comprehend. Isn’t that what we’re here for?
Steve “Woody” La Cerra is the front-of-house engineer and tour manager for Blue Öyster Cult. He can be reached via email at
Woody@fohonline.com
